A new non-Markovian stochastic Schrödinger equation at finite temperatures is presented to correctly describe charge carrier dynamics in organic molecular crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent complex-valued random fluctuations which are generated from corresponding spectral density functions. The approach is thus easily extended to investigate coherent-to-hopping charge transfer in systems with thousands of molecular sites. The capability of present approach is demonstrated by numerical simulations of carrier dynamics in the spin-boson model and a realistic Fenna-Matthews-Olson complex. The results manifest that the non-Markovian effect and complex-valued random forces are essential to guarantee the detailed balance. In an application to a long-chain donor-acceptor system, it is also interesting to find a property of coherent-to-hopping charge transfer from temperature dependence of diffusion coefficients.
A time-dependent wavepacket diffusion method is proposed to deal with charge transport in organic crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent fluctuations which are generated from the corresponding spectral density functions. The numerical demonstrations reveal that the present approach predicts the consistent charge carrier dynamics with the rigorous quantum approaches. In addition, the diffusion coefficients obtained from the Marcus formula are well reproduced at the weak electronic coupling and high temperature limits. It is also found that the charge mobility feature of the crossover from the band-like to the hopping-type cannot be predicted from the fluctuations induced by the linear electron-phonon interactions with an Ohmic spectral density; however, it indeed appears as the electronic coupling fluctuation exponentially depends on the nuclear coordinates. Finally, it should be noted that although the present approach neglects the imaginary fluctuation, it essentially incorporates the coherent motion of the charge carrier and quantum effect of the phonon motion with a broad regime of the fluctuations for symmetric systems. Besides, the approach can easily be applied to systems having thousands of sites, which allows one to investigate charge transport in nanoscale organic crystals.
Our research investigated the significant role of nuclear tunnelling and carrier delocalization effects in the charge transport process of organic semiconductors.
Aggregation‐caused fluorescence quenching with insufficient production of reactive oxygen species (ROS) has limited the application of photosensitizers (PSs) in fluorescence‐imaging‐guided photodynamic therapy (PDT). Aggregation‐induced emission PSs (AIE‐PSs) exhibit enhanced fluorescence intensity and a high efficiency of ROS generation in the aggregation state, which provides an opportunity to solve the above problems. Herein, a series of AIE‐PSs are successfully designed and synthesized by adjusting the D–A intensity through molecular engineering. The photophysical properties and theoretical calculations prove that the synergistic effect of 3,4‐ethylenedioxythiophene and quinolinium increases the intramolecular charge transfer effect (ICT) of the whole molecule and promotes the intersystem crossing (ISC) from the lowest excited singlet state (S1) to the lowest triplet state (T1). Among these AIE‐PSs, the optimal AIE‐PS (TPA‐DT‐Qy) exhibits the highest generation yield of 1O2 (5.3‐fold of Rose Bengal). Further PDT experiments show that the TPA‐DT‐Qy has a highly efficient photodynamic ablation of breast cancer cells (MCF‐7 and MDA‐MB‐231) under white light irradiation. Moreover, the photodynamic antibacterial study indicates that TPA‐DT‐Qy has the discrimination and excellent photodynamic inactivation of S. aureus. This work provides a feasible strategy for the molecular engineering of novel AIE‐PSs to improve the development of fluorescence‐imaging‐guided PDT.
The time-dependent wavepacket diffusion method for carrier quantum dynamics (Zhong and Zhao 2013 J. Chem. Phys. 138 014111), a truncated version of the stochastic Schrödinger equation/wavefunction approach that approximately satisfies the detailed balance principle and scales well with the size of the system, is applied to investigate the carrier transport in one-dimensional systems including both the static and dynamic disorders on site energies. The predicted diffusion coefficients with respect to temperature successfully bridge from bandlike to hopping-type transport. As demonstrated in paper I (Moix et al 2013 New J. Phys. 15 085010), the static disorder tends to localize the carrier, whereas the dynamic disorder induces carrier dynamics. For the weak dynamic disorder, the diffusion coefficients are temperature-independent (band-like property) at low temperatures, which is consistent with the prediction from the Redfield equation, and a linear dependence of the coefficient on temperature (hopping-type property) only appears at high temperatures. In the intermediate regime of dynamic disorder, the transition from band-like to hopping-type transport can be easily
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